Identification and partial purification of species-specific allergens from Triatoma protracta...

This article describes the immunochemical characterization of allergens from Triatoma protracta, a hematophagous insect that causes IgE-mediated anaphylactic reactions when it bites sensitized allergic persons. Comparison of the allergenic potency of T. protracta salivary gland extract, thoracic and abdominal hemolymph, and a whole body extract by RAST inhibition demonstrated that salivary glands were the main source of T. protracta allergens. Concentrated salivary gland extracts were purified by gel filtration and isoelectric focusing. Fractions were tested for allergenic activity by RAST inhibition and for protein purity by polyacrylamide gel electrophoresis and immunoelectrophoresis. Two protein peaks were obtained on gel filtration. The high-molecular-weight peak contained a 70,000 MW protein/glycoprotein that had little allergenic activity. The low-molecular-weight peak comprised six proteins, molecular weight 17,000 to 25,000, and T. protracta allergen(s) eluted in parallel with this peak. These proteins were resolved by isoelectric focusing, and two fractions, pI 6.7 to 7.3 and pI 8.2, contained most of the allergenic activity. By RAST, 25/28 sera from T. protracta-allergic patients contained IgE antibody to these fractions, suggesting that they were major allergens. Each fraction demonstrated a single precipitin arc on immunoelectrophoresis and two bands, molecular weight 18,000 to 20,000, on gel electrophoresis. Cross-inhibition radioimmunoassays demonstrated that each fraction completely inhibited binding of the other fraction to IgE antibody, suggesting that they contained different isoelectric forms of the same allergen.